Yes, in the stream options there was no layer map specified. I selected the auto option (screenshot attached) because I don't know how to access the layer map for the technology I am using. I already specified the technology. So, I got the GDS file and using the viewer it looks ok.
My followup question here, what is the file I need for Via Map in the stream options? because it's highlighted clearly that it would be better to add viaMap. what do you think?
Also, is there a way to count the number of transistors in my design?